Many surgical procedures entail the removal of tissue from the surgical site of operation, including various kinds of ophthalmological procedures. One example of a frequently performed procedure is cataract surgery. The instrument of choice for removing cataracts has been the phacoemulsification (“phaco”) device. Phaco technology utilizes ultrasound as the energy modality to fragment and remove the cataract. Specifically, phaco technology uses mechanical ultrasound energy to vibrate a small needle that fragments the cataract material. The needle is typically constructed of titanium, titanium alloy, or surgical-grade steel. During the procedure, aspiration is applied to remove the fragmented cataract material from the eye. Also during the procedure, irrigation fluid (e.g., saline solution) is applied to the eye to help maintain intraocular fluid pressure and neutralize the large amount of heat generated by the vibrating needle. A separate irrigation-aspiration instrument may be utilized, with vacuum applied to a central bore for aspiration and irrigation fluid supplied through an annular passage formed between the central bore and a coaxial sleeve surrounding the central bore. Alternatively, the phaco needle may be hollow to provide the aspiration function, and a separate instrument utilized for irrigation. As a further alternative, the phaco instrument may include a coaxial sleeve surrounding the hollowing needle, or one or more side outlets for irrigation fluid, thus performing both aspiration and irrigation in addition to tissue fragmentation. After the emulsified lens material is removed, it is replaced by an artificial intraocular lens (IOL) as appreciated by persons skilled in the art.
Phaco technology has some disadvantages. The high ultrasonic energy utilized may result in thermal damage to ocular tissue at the incision site. Moreover, the mechanical ultrasound energy delivered through the phaco needle creates a cavitation field that is intended, along with the mechanical movement of the tip, to fragment the cataract material. The cavitation may damage the iris or any ocular tissue or structure exposed to the cavitation. Hence, the surgeon must be very cautious when activating the ultrasound energy inside the eye. The broad propagation of ultrasonic waves and the cavitation are unavoidable consequences of the phaco technique; both are potentially harmful and currently are limitations of conventional phacoemulsification.
Moreover, the ultrasound energy created by the phaco device also is known to damage the endothelial cells, located on the inner lining of the cornea. These cells are critical for quality of vision. The harder the cataract, the greater the endothelial cell loss due to the higher level of ultrasound required to emulsify the cataract. It has been reported that in the use of phaco technology, there is an average endothelial cell loss of 13.74% (1.5 to 46.66%) with cataracts that are from a one-plus to a three-plus hardness. It has also been reported that there is an average endothelial cell loss of 26.06% (6.81 to 58.33%) when removing four-plus hardness cataracts with a phaco device.
Despite the foregoing limitations, phacoemulsification remains an effective technique for breaking up cataract material, particularly cataract material having relatively high hardness (four-plus or higher). There is a need, however, for providing techniques effective for tissue fragmentation and removal based on modalities other than phacoemulsification. There is a need for providing such techniques as alternatives to phacoemulsification or for implementation in combination with phacoemulsification.